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| author | Ian Abbott <abbotti@mev.co.uk> | 2014-10-20 15:10:40 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-11-14 10:10:37 -0800 |
| commit | 2894a3a2bcb91959207376484c6c4d01ce605e73 (patch) | |
| tree | 8d42ce5c009b2bbe8b7a39334e550dd639e6bb3a | |
| parent | 50b784c20405c44f5d3b3444dc66915d4901f790 (diff) | |
| download | lwn-2894a3a2bcb91959207376484c6c4d01ce605e73.tar.gz lwn-2894a3a2bcb91959207376484c6c4d01ce605e73.zip | |
staging: comedi: fix memory leak / bad pointer freeing for chanlist
commit 238b5ad855924919e5b98d0c772d9dc78795639b upstream.
As a follow-up to commit 6cab7a37f5c04 ("staging: comedi: (regression)
channel list must be set for COMEDI_CMD ioctl"), Hartley Sweeten pointed
out another couple of bugs stemming from commit 6cab7a37f5c04 ("staging:
comedi: comedi_fops: introduce __comedi_get_user_chanlist()").
Firstly, `do_cmdtest_ioctl()` never frees the kernel copy of the user
chanlist allocated by `__comedi_get_user_chanlist()`, so that memory is
leaked. Fix it by freeing the allocated kernel memory pointed to by
`cmd.chanlist` before that pointer is overwritten with its original
pointer to user memory before `cmd` is copied back to user-space.
Secondly, if `__comedi_get_user_chanlist()` returns an error,
`cmd->chanlist` is left unchanged and in fact will be a pointer to user
memory. This causes `do_cmd_ioctl()` to `goto cleanup` and call
`do_become_nonbusy()` which would attempt to free the memory pointed to
by the user-space pointer. Fix it by setting `cmd->chanlist` to NULL at
the start of `__comedi_get_user_chanlist()`.
Fixes: c6cd0eefb27b ("staging: comedi: comedi_fops: introduce __comedi_get_user_chanlist()")
Reported-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/staging/comedi/comedi_fops.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index d9c6f4c21ce7..7a2e9c023257 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1462,6 +1462,7 @@ static int __comedi_get_user_chanlist(struct comedi_device *dev, unsigned int *chanlist; int ret; + cmd->chanlist = NULL; chanlist = memdup_user(user_chanlist, cmd->chanlist_len * sizeof(unsigned int)); if (IS_ERR(chanlist)) @@ -1615,6 +1616,8 @@ static int do_cmdtest_ioctl(struct comedi_device *dev, ret = s->do_cmdtest(dev, s, &cmd); + kfree(cmd.chanlist); /* free kernel copy of user chanlist */ + /* restore chanlist pointer before copying back */ cmd.chanlist = (unsigned int __force *)user_chanlist; |